Is it not just a pressure vessel between the ribs? So basically hoops stress. The tangential hoop stress would be q*r/t where q is pressure and r is radius of curvature and t is thickness. The radial displacement would be 0.85*qr/(Et) .... assuming mu = 0.3. Am i missing something?Does anyone have an analytical method and coefficients for curved plates under pressure so that we might validate Stanislavz's FEA work?